Extremely repetivite and boring...voice acting is head-splitting.
There's also little things that will drive you crazy, like that of all the characters repeating the same phrases over and over and over and over and over. Also, the bugginess mentioned above--it's pretty bad. You'll get stuck in objects, walls, you name it. You'll get killed from all over the place, and sometimes powerups or items just won't work.
In other words, this is another 3D platformer with a liscense slapped on it. I wouldn't recommend buying unless you're an extremely obsessive PSX collector.